Dosimeters are a radiation measurement device and a frequently used in the nuclear field. A dosimeter generally contains a passive device for measurement of radiation exposure, and also contains encoded data in the form of punchcodes, reflecting identification information on the dosimeter. In one respect, the dosimeter can be considered to be a modern version of the "film badge" where identifying information is printed on the outside of the film packet. In a dosimeter, reading the encoded punchcode data provides a similar type of identification information.
As a radiation measurement device, dosimeters are used in personnel protection in the nuclear industry, such as for use in nuclear power plants, infacilities that work with nuclear materials, within the medical profession, and in some cases in environmental radiation situations, such as in uranium mining and milling. In dosimeters of the type with which the invention is concerned, a punchcode is punched into hole positions in two rows that run along one side of the dosimeter, with the punchcode being used as a mechanical means of encoding data, such as identification of the individual or of an assigned unit. The punchcode can be read and displayed by a reader in conjunction with computer-based processing equipment.
There are several manufacturers that use a punchcode array with their dosimeters and one example is the Panasonic Model UD-800 dosimeter. Conventional readers, including those used for reading ht Panasonic Model UD-800 dosimeter, read encoded data, i.e., the punchcode data, by using multiple photosensors. Generally speaking, the dosimeter is mechanically positioned over a photosensor array, and the punchcode holes are detected.
The use of photosensors to read data encoded on a punched card is, of course, conventional. For example, U.S. Pat. No. 3,758,754 describes a reader device which uses light-emitting diodes in conjunction with photodiodes to provide optical reading of a card as the card is passed through a slot containing the photosensor elements. The same patient also discloses the use of encodable data positions int eh form of punched holes arranged in rows on the card that are read by the optical reader elements. However, it is necessary with this device that the card containing the coded data be inserted in a slot in a particular manner, and be moved by the operator to the opposite end of the slot. Not only does this take significant time and require operator involvement to move the card through the equipment, but it does not provide a controlled movement of the card, and requires a specific positioning of the card to function effectively. The lack of a controlled movement of the card lends to limited readability functions, e.g., only "ready" or "fail," and prevents more fully automated reading of the coded data for processing of more detailed card information, such as being able to read closed as well as open hole positions.
Other dosimeter reading equipment require that the dosimeter be taken by a piece of equipment and mechanically fit into a slot, e.g., by use of motors that drive the dosimeter into position, where it is then moved by appropriate apparats through the reader. This is a fairly slow process if one is doing stand-alone reading of thousands of these dosimeters. Also, the mechanical positioning of the dosimeter in the reader is not only time-consuming, but involves mechanical operations that require periodic maintenance and generate reliability problems. Furthermore, existing types of punchcode readers are often found incorporated in other pieces of equipment, which is disadvantageous in terms of the flexibility in use and the portability of the equipment.
Numerous other systems and devices have been described for reading data by means of optical sensors or card reader type of devices. However, such devices generally involve complicated mechanical assemblies, and require an undesired amount of operator involvement. A punchcode reader that is able to read significant amounts of encoded data from a dosimeter is thus desirable and the need exists for a reader adapted to use with a dosimeter that would read punchcodes electronically, and do this in a rapid, yet simple manner, without the disadvantages in terms of speed and mechanical complexity associated with presently available dosimeter readers.